This invention relates to the field of agricultural and horticultural production in greenhouses, and more particularly to greenhouses adapted for uninterrupted year round production, having an independent fuel source for heating, and exhaust gas fertilization. The invention also relates to the field of co-generation of electrical power for artificial lighting, and other power needs of a greenhouse, as well as for providing heat in the wintertime for the greenhouse and excess electrical power to the grid in the summertime.
Greenhouses have been designed to extend the growing season and to enhance plant growth. Enhancement techniques have included the use of programmed artificial lighting, hydroponic systems for root support and feeding of nutrients, enrichment of the air in the greenhouse enclosure with CO2, heating the greenhouse in cold weather, cooling it in hot weather, and using computers to control the environment to suit the type of plant being grown.
The cost of energy required to support a year round greenhouse is significant, especially in a cold climate. Proposals have been made to use methane-rich landfill gas as an energy source, both because of its lower cost and because of the beneficial environmental effects of removing methane from otherwise escaping into the atmosphere, where it is known to harm the ozone layer.
U.S. Pat. No. 6,205,704, issued Mar. 27, 2001 to Schmitz et al describes a method and apparatus for an environmentally controlled greenhouse located near a landfill site, comprising collecting landfill gas (LFG) from the landfill, transporting the landfill gas, distributing a first LFG portion of the landfill gas to a combustion system, heating a heat exchange fluid with the products of combustion, and controlling the temperature of growing plants in the greenhouse with the heat exchange fluid, distributing a second LFG portion of the landfill gas to a CO2 system, where the non-methane hydrocarbons (NMO) and reduced sulfur compounds (TRS) are adsorbed from the LFG prior to a controlled combustion which removes methane and generates a clean CO2 system product gas (CSPG), conducting the CSPG to the greenhouse enclosure, and selectively controlling the temperature and the carbon dioxide level in the greenhouse. In a preferred embodiment, a portion of the CO2 system product is mixed with air and used to regenerate dual-connected adsorber beds used to remove the NMO""s from the second LFG portion. A modified system interposes a turbine generator to recover additional energy from the combustion of the first LFG portion and uses steam extracted from the turbine to heat the greenhouse. The Schmitz patent uses a centralized LFG collection system for the landfill, in which all of the LFG is transported to a central collection point and divided into separate portions for heating and CO2 fertilization purposes.
Small gas turbine generators have been developed, which generate electrical power for either stand alone distributed power, or for connection to the electrical power grid. The hot exhaust gases are directly usable for various co-generation purposes, such as water or air heating, absorption cooling, or industrial uses requiring heat. Gas turbine exhaust with low emission ratings of NOx has been successfully used to heat greenhouses by a MicroTurbine(trademark) (trademark of the Capstone Turbine Corporation) by exhausting the gas directly into the greenhouse.
Briefly stated, the invention comprises a greenhouse system with co-generation power supply, heating, and exhaust gas fertilization for operation with a source of hydrocarbon fuel, the greenhouse system comprising a gas turbine connected to the fuel source providing a hot exhaust gas containing CO2, NOx and SOx, an electric generator driven by the gas turbine, a greenhouse for growing plants and utilizing a number of power consuming devices supplied by the electric generator, a heat exchange system for heating the greenhouse with the hot exhaust gas, an exhaust gas treatment system receiving the hot exhaust gas, and a fertilization system for fertilizing the plants with the products from the gas treatment system.
In a preferred embodiment, a number of such greenhouse systems are located on a landfill site generating landfill gas (LFG) containing methane and CO2, where the source of the fuel for the gas turbines is LFG from individual wells drilled in the landfill. The generators are connected to service the power consuming devices of their respective greenhouses. They are also provided with an interconnection to the electrical grid maintained by the utility company, so as to enable supply of excess power to the grid and to receive power from the grid. In the preferred embodiment, the gas treatment system cleans the gas for direct CO2 fertilization. The NOx and SOx from the treated gas are converted and react with other substances in a fertilizer conversion system to provide fertilizer for enhancing growth of the greenhouse plants.